A Study on the Physical Properties of Polycarbonate/Acrylonitrile-Butadiene-Styrene Blends with Various Thermal Stabilizers to Secure the Safety of Automobile Passengers

Deterioration of polymer materials can cause breakdown of various automobile parts during their life cycles, which is a threat to the safety of occupants. In the research described here various thermal stabilizers were incorporated into polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends, often used in automotive parts, to investigate the thermal degradation of PC/ABS as a function of mixing rate and mixing time and as a function of stabilizer type and content. A phenolic stabilizer, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (S1) and two kinds of phosphite stabilizers, tris-(2,4-di-tert-butyl-phenyl phosphite) (S2) and bis(2,4-dicumylphenyl) pentaerythritol diphosphite (S3) were used. Thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) results showed that high mixing rates, over 2000 rpm, caused high shear heating, which brought about thermal degradation of the polymer blends. The S3 better prevented thermal degradation of the PC/ABS blends during high speed processing compared to the other stabilizers. Characterization of the mechanical properties of the blends prepared at a screw speed of 1000 rpm for 20 sec indicated decreases in elongation at break from 148% prior to processing to 63% for S1, 108% for S2 and 131% for S3, whereas the tensile strengths showed only slight changes. Scanning electron microscope (SEM) images indicated that the size distribution of the dispersed phase was decreased with increasing screw speed and mixing time. The interfacial tension of the blends decreased with increasing mixing rate, whereas it did not exhibit significant change with increasing mixing time.